1. Field of the Invention
The present invention relates to a switch mechanism utilized in security interface devices such as keypad installations to render them tamper-resistant, wherein the devices are generally connected to burglar alarm and fire alarm systems.
More particularly, the present invention pertains to the provision of a conductive tamper switch which is installed in a security interface device, such as a keypad, which upon an unauthorized attempt to dislodge the device or keypad from a wall or surface on which it is mounted, will trigger an alarm or generate a warning signal at a monitoring site indicative that an effort at tampering with the device has been effected.
Currently, security interface devices, such as those which consist of keypad units, are normally mounted on the walls or other upright surfaces of the most diverse locations, such as in homes, apartments, offices and manufacturing sites and plants. The security interface devices are frequently equipped with tamper-indicating structures. For instance, such structures may comprises tamper switches installed in the keypads, and among other locales, which may contact electronic operative components contained in the keypad housings, such as printed circuit boards (PCBs). However, presently employed tamper-indicating structures may be sensitive to noises such as mounting surface conditions, the skill of an installer, the proper assembly of a tamper switch and keypad enclosure, and may even be unduly sensitive to external environmental and weather conditions. For example, upon the installation of a security interface device, such as a keypad, on a wall surface which is subject to uneven surface mounting properties, it is possible that a tamper post contained in the housing, wherein the tamper post is intended to be in contact with electronic circuitry on a printed circuit board located in the keypad housing may be offset and misaligned from a tamper switch on the printed circuit board subsequent to the installation of the keypad, thereby leading to potential tamper detecting malfunctions. Consequently, the personnel or installers which are engaged in mounting the security interface devices must be capable of properly implementing any necessary adjustments to either the security interface device or to the surface of the wall in order to be able to ensure the reliable functioning thereof in connection with the tamper-detecting mechanism subsequent to installation of the device.
Such tamper-detecting devices have heretofore been comprised of plastic or rubber posts or metallic spring members, which are mounted interiorly of the keypad housing and extend from the back housing portion forwardly into contact with a tamper switch or contact located on a printed circuit board contained within the keypad housing, whereby any attempt to pull the keypad device from the wall in an unauthorized manner will cause a disengagement between contacts formed by the tamper post or spring and a tamper switch mounted on the printed circuit board or to rupture a segment of the back housing mounting the tamper post, so as to produce a short circuit in the electronic system of the printed circuit board and to consequently trigger a signal raising an audible alarm and/or notifying a remote location which monitors the function of the keyboard or the security device, such as at an alarm company or law protective agency.
Moreover, this type of prior art structure, upon the unauthorized pulling off the front cover portion of the keypad housing, will trigger an alarm signifying that tampering has occurred, but is not adapted to provide a disconnection between the printed circuit board and the tamper post or spring which activates the tamper switch when the keypad housing is pulled away from the wall in its entirety, rather than merely the front housing part, unless the frangible segment of the back casing of the housing is ruptured, which segment is fastened to the wall, whereby the tamper post which is mounted on that segment and normally contacts the tamper switch on the printed circuit board, is concurrently pulled away from the printed circuit board so as to break contact therewith. This, of course, in due course requires replacement of the damaged rear portion of the keypad housing for reuse thereof. Thus, a good installation, which incorporates a tamper switch or mechanism utilized in the security interface device, such as a wall or surface mounted keypad, not only requires an assured reliability in reporting any tampering, but in addition to such functional requirements should also be cost effective in the manufacture, installation and utilization thereof in service over a lengthy service life.
2. Discussion of the Prior Art
Clark, U.S. Pat. No. 6,016,677 discloses a keypad for a door lock including a tamper detection and response feature whereby the unauthorized removal of a part or a front portion of the keypad, which forms a component of a deadbolt lock will activate a sensor switch utilized on a push/pull lock arrangement. This provides that the lock is automatically relocked when the mechanism is in a secured position, and in which whereby the system of the keypad provides for a remote enable and disable unit, directs a detection and a response unit, a low battery sensing arrangement, includes a bolt extension indicating feature and adjustable bolt throw feature. This is a relatively complex configuration, which does not readily lend itself to a simple tamper indicating switch mechanism which is incorporated in a wall or surface mounted keypad security device.
Magner, et al., U.S. Patent Publication No. 2005/0140496 A1 discloses a keypad and method providing for electronic access security and keyless entry of a vehicle. In that instance, there is disclosed a keypad for the keyless entry of the vehicle, including a coded arrangement. However, this particular structure does not incorporate a tamper-indicating feature analogous to that contemplated for by the present invention.
With regard to Hom, et al., U.S. Patent Publication No. 2003/0227766 A1, there is disclosed a keypad system including an illumination arrangement and light from LEDs which signify activation thereof. Again, there is no tamper indicating switch structure contacting a printed circuit board analogous to that employed in the present invention.